The long-term goal of this revised competing continuation ROl application is to understand the functional basis for the diversity and presence of the unique fiber-forming collagen systems in vertebrate organisms. This research addresses two general questions; first, why there are so many fiber-forming collagen types; and second, why the distribution of each type is tissue-specific. This application focuses on type III collagen as a model system to determine the structural and functional basis for the unique distribution of this collagen in different human tissues. The Principal Investigator has recently described a rapid and sensitive technique relying on high pressure liquid chromatography (HPLC) for the resolution and quantitation of a small marker peptide for each collagen. The Specific Aims are: first, to test the hypothesis that the proportions of type III collagen are elevated in distensible tissues. The recently described HPLC technique will be used to determine the proportions of type I and III collagens from defined regions in human thoracic aorta (highly distensible) and abdominal aorta (less compliant) derived from young men and women. The method depends on the detection of the alphal(I)-CB2, alphal(III)- CB2, and alphal(V)-CBI cyanogen bromide peptides. The type III collagen content of highly distensible human thoracic aorta and noncompliant aorta samples will be determined. This study should test the hypothesis that type III collagen is more prevalent in distensible tissues. The second specific aim is to establish the role of type III collagen as a major contributor, along with type II collagen, to the biological function of a nondistensible tissue. HPLC will be used to develop a comparable analytical system for determining the proportions of fiber-forming collagens in hyaline cartilage samples, i.e., type II, III, IX and XI collagens. The third specific aim is to test the hypothesis that a major alternative role of type III collagen is to facilitate binding of a novel inhibitor of serine proteases termed short peptide from alpha l-antitrypsin (SPAAT) to extracellular matrices. This binding enables at least type III collagen, and possibly other macromolecules, to resist inappropriate attack by serine proteases. The functional role of the preferential binding of a SPAAT to type III collagen will be determined by evaluating the ability of the active fragment of SPAAT to the fiber-forming collagens to inhibit degradation of type III collagen fibrils formed in vitro. The fourth specific aim is to test the hypothesis that SPAAT will be localized largely in tissues rich in type III collagen.Tissue distribution of SPAAT will be evaluated by immunohistochemical techniques using specific antibodies.